dog eat dog意思是残酷无情的竞争；同室操戈；互相伤害；残酷无情的竞争；自相残杀。

【例句】
Calm down，“Dog eat dog” could not solve the problem.
冷静，互相伤害并不能解决问题。

I'm afraid in this line of work it's a case of dog eat dog.
恐怕在这种行业中竞争是残酷无情的。